The HIV-1/AIDS epidemic continues to spread worldwide, despite considerable efforts to control it. In 2006 approximately 40 million people were living with HIV, 2.6 million more than in 2004, with sub-Saharan Africa and the Indian subcontinent bearing the brunt of the global epidemic. In North America and Western Europe, however, the advent of combination antiretroviral drug regimens have proven remarkably successful at controlling HIV-1 infection and have resulted in significant reductions in morbidity and mortality from AIDS. Despite these successes, new targets for inhibition of HIV-1 replication are highly desirable, and new drugs will be needed to combat the rising problem of anti-retroviral drug resistance. Lentiviruses, including HIV-1, are unusual in having transmembrane glycoproteins with much longer cytoplasmic domains than other retroviruses, suggesting an essential role in the lifecycle of the virus. Several studies have demonstrated that the gp41 cytoplasmic (gp41c) domain exerts an effect on the incorporation of Env into virions, with the interaction of the gp41c domain with the Matrix (p17) portion of Gag being essential for effective incorporation. This interaction is mediated by a host cell factor, Tail Interacting Protein of 47kDa (TIP47). Silencing of cellular levels of TIP47, or overproduction of a ?-galactosidase-gp41c fusion protein in cells used to produce virus have been found to have a negative effect on Env incorporation, producing virions with greatly reduced infectivity. Given these observations, we believe that disruption of either or both the HIV-1 gp41c domain- TIP47 and TIP47-Matrix interactions will result in the production of less infectious virus and that these interactions are viable targets for therapeutic intervention. Moreover, motifs involved in these interactions are broadly conserved across HIV-1 subtypes, suggesting that targeting of these previously unexploited interactions could yield a broad-spectrum antiretroviral agent that may be able to withstand the mutability of HIV-1. Therefore, we propose pilot studies to allow the investigation of this hypothesis. A two-tiered research approach is proposed involving mutagenesis and interaction analysis by surface plasmon resonance (SPR) to determine interfaces between interacting components (Specific Aim 1), and then based upon this epitope identification, development of a FRET-based assay to allow the cost-effective, high-throughput screening of compounds that disrupt these interactions (Specific Aim 2). The proposed studies will provide the foundation for inhibitory compound identification, in addition to generating reagents that could be used for the structural characterization of the TIP47-Matrix and TIP47-gp41c domain complexes. It is our hope that, collectively, these results and the results from subsequent studies will define these interactions as viable therapeutic targets and will drive the design of novel inhibitors targeting these complexes. Combination antiretroviral drug regimens have proven remarkably successful at controlling HIV-1 infection in the Western world. Despite this success, new targets for inhibition of HIV-1 replication are highly desirable, and new drugs are needed to combat the rising problem of drug resistance. The experiments proposed in this application will serve as a platform to explore the therapeutic potential of a previously unexploited process in the HIV-1 lifecycle. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]